1. Field of the Invention
The invention relates to arrangements for providing all combustion air from at least a predetermined distance above a floor on which a gas, or other fuel-fired, water heater is installed so as to prevent dense flammable vapors from spreading along the floor and entering the burner area of the heater. More particularly, the invention relates to such arrangements that are compatible with being retrofitted to a previously installed water heater.
2. Background Information
Most conventional gas-fired water heaters comprise a generally cylindrical housing adapted to be placed upon a floor. A heater of this sort has a combustion chamber located near the floor of a base portion or body thereof, and also has an air inlet located adjacent the combustion chamber and very near the floor in order to provide a source of air to the combustion chamber. This type of design is logical because it allows a water tank to be conveniently located above a burner located adjacent the floor on which the water heater is installed. The air inlet is normally located near the combustion chamber burner for simplicity of construction.
In some circumstances, flammable fluids such as gasoline, dry cleaning fluids, kerosene or paint thinner may be used in a room where a gas-fired water heater is located. If any significant accumulation of fumes from these types of flammable liquids builds up in a room, the fumes, which are more dense than the air, and therefore generally tend to remain near the floor of a room, or the liquids themselves, may provide a flammable or explosive mixture within the water heater""s combustion chamber.
Numerous solutions have been proposed to avoid this fire hazard. Some of these require structural modifications to the room in which the water heater is installed as well as affecting the location of plumbing and fuel line connections to the heater. Examples of such approaches include installing the water heater on a pedestal, or bringing combustion air in from outside the room, as taught by Smith in U.S. Pat. No. 5,341,767. These approaches are sometimes compatible with new construction, but are too expensive if applied to either an existing water heater or to installation of a replacement water heater.
Other solutions to the fire hazard problem have required substantial redesign of the heater itself. These approaches may be applicable to newly purchased water heaters, but are of no use in considering how to safeguard an existing water heater. Solutions in this category include the teaching of
Moore, Jr., et al. in U.S. Pat. No. 4,940,042, who provide air inlet ports at the top of a water heater housing,
Valcic, et al., in U.S. Pat. No. 6,135,061 who provide an air inlet port having a flame arrestor installed thereon; and of
Lopez in U.S. Pat. No. 5,690,061, who raises the combustion chamber above a predetermined height by adding an expansion chamber at the bottom of the water heater""s housing.
Several solutions to the water heater fire hazard problem have been proposed that do not require modification of the heater design or of the installation location. Notable patent references providing teaching in this area are:
U.S. Pat. No. 5,085,205, wherein Hall, et al. describe installing the heater in a bucket-like enclosure. Their enclosure incorporates a water drain and an access door aligned with the existing access door for lighting the pilot flame. Because their enclosure has to be placed on the floor before the heater is lowered into place, it can generally only be used when one is installing a new heater.
U.S. Pat. No. 5,765,547 to LaPlante, who shows a hinged collar that can be clamped around an already-installed heater and sealed to the floor.
U.S. Pat. No. 5,848,586, to Garms, who shows a double collar that reportedly provides better inlet air flow than does LaPlante""s.
U.S. Pat. No. 5,918,591 to Vollmar et al., who improve on the enclosures shown by Hall et al. and by LaPlante by allowing for installation around an already-installed heater without requiring caulking the bottom of the collar to the floor.
U.S. Pat. No. 6,058,892, to Haack, II, who teaches the use of a collar clamped around the bottom of a water heater so as to close off the air inlets provided by the manufacturer. One or more air inlet tubes feed through the collar and into the combustion chamber. There may be a separate door, like Hall""s, for accessing the pilot flame.
An object of the invention is to provide apparatus and method for preventing fires and explosions caused by the ingress of liquids and relatively dense flammable vapors into the burner area of a fuel-fired water heater. In a preferred embodiment, all air inlets except for a pilot flame access doorway are blocked and an inlet apparatus is fitted over the pilot access doorway so as to supply all combustion air from a selected height above the access doorway. In a preferred embodiment, the inlet apparatus comprises a tube that can be installed in a vertical orientation so that a flange portion at a lower end of the apparatus abuts, or nearly abuts, the water heater housing around the access doorway. The flange portion has a size and shape selected so that it fits over the pilot flame access doorway in a sealing relationship allowing air to pass through the access doorway only if it first passes through the inlet tube. In particular preferred arrangements, the inlet apparatus comprises a gasket having a size and shape selected to be captured between the flange and a portion of the water heater housing immediately adjacent the access doorway. The inlet apparatus may also comprise at least one mechanical fastener, such as one or more threaded fasteners or one or more spring clip(s), usable for holding the flange against the water heater housing. In addition, a flame arrestor screen may be secured over the inlet end of the inlet tube.
It is a particular object of the invention to provide retrofit apparatus and method for bringing all combustion air from at least a predetermined height to a burner of a fluid-fueled water heater previously installed on the floor, where the apparatus and method are arranged to ensure that all the combustion air is constrained to pass through a pilot flame access doorway formed in a housing of the water heater.
A feature of apparatus of the invention used to bring combustion air from at least a predetermined height above a floor and to pass that air through a pilot flame access doorway in the housing of a fuel-fired water heater is its compatibility with various arrangements for obscuring or otherwise sealing off all other paths for air access to the burner.